The proposed research continues my morphological studies on the neurotrophic phenomenon in amphibian limb regeneration, on interactions between the axon and its enveloping glial sheath, and on the role of ependyma in patterning the developing CNS tracts and nerve roots. In the neurotrophic studies our immediate plans are to pursue further the reaction of regenerate cells to the nervous agent by studying the effect of denervation on the polysomal profile, on histone phosphorylation and on the spectrum of proteins synthesized. In addition we will continue our studies on the nature of the nervous agent, using in this case a new assay method for identifying the active nervous fractions, namely the mitogenic effect on embryonic chick myoblasts in vitro. Our past successful efforts in demonstrating the transport of substances through the myelin sheath, particularly the Schmidt-Lanterman clefts, will be pursued using electron probe analyses for elemental ions in the cleft which we believe are sequestered there. In the case of the ependyma we observed that ependymal processes in the regenerating spinal cord of the newt form channels which are then invaded by growing axons. We will extend these observations to studies on the embryonic CNS to see if channels also pattern embryonic axonal growth. IDEN*